Method of manufacturing scintillator panel, scintillator panel, and radiation image detector

ABSTRACT

A method of manufacturing a scintillator panel in which no dust is generated when improving protrusions on the phosphor surface, resulting in no generation of image defects caused by the dust, to-provide a scintillator panel exhibiting excellent image quality and a radiation image detector thereof. The scintillator panel includes a support having a phosphor layer formed thereon. The method includes forming the phosphor layer on the support, and subsequently heat-treating the support and the phosphor layer which are sandwiched by two rigid plates under applied pressure.

This application is a U.S. National Phase Application under 35 USC 371of International Application PCT/JP2010/053977 filed Mar. 10, 2010.

TECHNICAL FIELD

The present invention relates to a method of manufacturing ascintillator panel, and the scintillator panel and a radiation imagedetector.

BACKGROUND

In the past, radiation images such as X-ray images have been widely usedfor diagnosing disease in clinical practice. Specifically, over a longperiod of history, radiation images formed via an intensifyingscreen-film system have accomplished high sensitivity and high imagequality, whereby they are still utilized in clinical practice all overthe world as an imaging system exhibiting high reliability and excellentcost performance at the same time. However, since the above-describedimage information is so-called analogue image information, and neitherfree image processing nor instantaneous electric transmission can bemade in the similar way as in digital image information having been inprogress in recent years.

Further, in recent years, a digital system radiation image detector,typified by computed radiography (CR) or the like has appeared. Sincedirect formation of digital radiation images is obtained by these andimages can be directly displayed on an image display device such as acathode tube, a liquid crystal panel or the like, the images are notnecessarily formed on a photographic film. As a result, theabove-described digital system X-ray image detector has reduced the needof image formation via a silver halide photographic system, and hassignificantly improved convenience of diagnostic action in hospitals andclinics. This computed radiography (CR) has been accepted at present inclinical practice, but not only sharpness is insufficient, but alsospace resolution is insufficient, whereby it has not achieved the samelevel as in a screen•film system.

On the other hand, further, a flat panel type radiation image detector(Flat Panel Detector: FPD) fitted with thin-film transistor (TFT) hasbeen developed, for example, as a new digital X-ray image technology.

A scintillator panel made from X-ray phosphor exhibiting an emissiveproperty produced by radiation in this flat panel type radiation imagedetector to convert radiation into visible light, but the use of ascintillator panel exhibiting high emission efficiency should be used inorder to improve an SN ratio in radiography at a low dose. Generally,the emission efficiency of a scintillator panel depends on thickness ofa phosphor layer (scintillator panel layer) and X-ray absorbance of thephosphor, but a thicker phosphor layer causes more scattering ofluminescent light within the phosphor layer, resulting in loweredsharpness. Accordingly, sharpness desired for image quality determinesthe layer thickness.

Specifically, since cesium iodide (CsI) exhibits a relatively highconversion ratio of from X-rays to visible light, and a columnar crystalstructure of the phosphor can readily be formed through vapordeposition, light guide effect inhibits scattering of luminescent lightwithin the crystal, enabling an increase of the phosphor layerthickness.

However, since in the case of use of CsI alone, emission efficiency islow, one in which a mixture of CsI with sodium iodide (NaI) at anymixing ratio is deposited on a substrate via evaporation assodium-activated cesium iodide (CsI:Na), or recently, one in which amixture of CsI with thallium iodide (TlI) at any mixing ratio isdeposited on a substrate via evaporation as thallium-activated cesiumiodide (CsI:Tl) is subjected to annealing as a post-treatment to improvevisible conversion efficiency, and the resulting is used as an X-rayphosphor.

As a method of manufacturing a scintillator panel, known is a method offorming a phosphor on a support such as an aluminum plate, an amorphouscarbon plate or the like. In the case of the method of manufacturing ascintillator panel, it is generally known that deposited phosphorcrystals caused by defects, dust and so forth on the support are anomalygrown, whereby protrusions are generated on the phosphor surface. Sincesuch protrusions cause image defects, this should be improved.

As to the protrusions generated on such a phosphor surface, known aretechniques of planarizing protrusions by squashing them with a jig,grinding them with a grinder for removal, cutting them with a cuttingmeans, or the like (refer to Patent Document 1, for example).

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Patent O.P.I. (Open to Public Inspection)Publication No. 2002-243859

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, since those described in the above-described Patent Document 1are associated with deformation of protrusions and fracture caused byremoval of the protrusions, phosphor dust is generated. It is difficultto completely eliminate this dust, and output of a photoelectricconversion element in response to phosphor becomes inaccurate because ofthe dust remaining on the phosphor, leading to image defects, wherebyproduced is a problem such that it interferes with reproducibility ofaccurate radiation images.

The present invention has been made on the basis of the above-describedproblem, and it is an object of the present invention to provide amethod of manufacturing a scintillator panel in which no dust isgenerated when improving protrusions on the phosphor surface, resultingin no generation of image defects caused by the dust, and to provide ascintillator panel exhibiting excellent image quality and a radiationimage detector thereof.

Means to Solve the Problems

The above-described problem is accomplished by the following structures.

(Structure 1) A method of manufacturing a scintillator panel comprisinga support and formed thereon, a phosphor layer, comprising the steps offorming the phosphor layer on the support, and subsequentlyheat-treating the support and the phosphor layer while the support andthe phosphor layer are sandwiched by two rigid plates under appliedpressure.

(Structure 2) A method of manufacturing a scintillator panel comprisinga support exhibiting stiffness and formed thereon, a phosphor layer,comprising the steps of forming the phosphor layer on the support, andsubsequently heat-treating the phosphor layer while the phosphor layeris sandwiched by the support and a rigid plate under applied pressure.

(Structure 3) The method of Structure 1 or 2, wherein the scintillatorpanel comprises a resin section excluding the phosphor layer, having atotal thickness of 10 μm or more.

(Structure 4) The method of any one of Structures 1-3, wherein thesupport comprises polyimide as a main component.

(Structure 5) The method of any one of Structures 1-4, comprising thesteps of storing the support and the phosphor layer while the supportand the phosphor layer are sandwiched by the two rigid plates, orstoring the phosphor layer while the phosphor layer is sandwiched by thesupport and the rigid plate in a plastic film container; and sealing anddepressurizing the plastic film container to conduct the appliedpressure.

(Structure 6) The method of any one of Structures 1-5, comprising thestep of covering the phosphor layer by a protective layer.

(Structure 7) The method of Structure 6, wherein the protective layercomprises a resin film.

(Structure 8) The method of Structure 6, wherein the protective layercomprises a polyparaxylene resin film formed by a CVD method.

(Structure 9) The method of any one of Structures 1-8, wherein thephosphor layer comprises columnar crystals.

(Structure 10) The method of Structure 9, comprising the step ofevaporating cesium iodide and an additive containing a thallium compoundas raw materials to form the phosphor layer.

(Structure 11) A scintillator panel prepared by the method of any one ofStructure 1-10.

(Structure 12) A radiation image detector comprising the scintillatorpanel of Structure 11 attached onto a photoelectric conversion panelcomprising a photoelectric conversion element.

That is, in the case of the present invention, protrusions caused byanomalous growth of evaporated phosphor crystals, which are originatedfrom dust or the like, are displaced to the resin layer side with nodeformation to get stuck in the resin layer by conducting a sandwichingstep with two rigid plates after forming a phosphor later andheat-treating the resulting under applied pressure to flatten thesurface of the phosphor layer.

Effect of the Invention

By utilizing the present invention, it is possible to provide a methodof manufacturing a scintillator panel in which no dust is generated whenimproving protrusions on the phosphor surface, resulting in nogeneration of image defects caused by the dust. This makes it possibleto provide a scintillator panel exhibiting excellent image quality and aradiation image detector thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart showing an outline procedure to prepare ascintillator panel relating to the present embodiment.

FIGS. 2 a, 2 b and 2 c are diagrams showing preparation procedures of ascintillator panel relating to the present embodiment.

FIGS. 3 a, 3 b, 3 c and 3 d are diagrams showing other preparationprocedures of a scintillator panel relating to the present embodiment.

FIG. 4 is a diagram showing an outline structure of an evaporator.

FIG. 5 is an oblique perspective view accompanied with a partlybroken-out section showing an outline structure of a radiation imagedetector.

FIG. 6 an enlarged cross-sectional view of an imaging panel section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, the present invention will be described in detail employing thepresent embodiments, but the present invention is not limited thereto.

FIG. 1 is a flowchart showing an outline procedure to prepare ascintillator panel relating to the present embodiment.

As to a scintillator panel in the present embodiment, a reflection layeris first formed on a support (Step S101), and a subbing layer issubsequently formed on the reflection layer (Step S102). Further, aftera phosphor layer is formed on the subbing layer (Step S103), protrusionsas defects generated on the phosphor layer are repaired (Step S104).Thereafter, a protective layer is formed so as to cover the phosphorlayer (Step S105) to prepare a scintillator panel.

The scintillator panel prepared in accordance with the above-describedprocedure is attached onto a photoelectric conversion panel fitted witha photoelectric conversion element to prepare a radiation imagedetector.

In addition, repairing of protrusions (Step S104) and formation of aprotective layer (Step S105) may be conducted in reverse order. As tothe following FIGS. 2 a, 2 b and 2 c, and FIGS. 3 a, 3 b, 3 c and 3 d,explanation will be made employing an example of the case when aprotective layer is formed.

Next, each step of the flowchart shown in FIG. 1 will be described indetail.

FIGS. 2 a, 2 b and 2 c are diagrams showing preparation procedures ofscintillator panel 10 relating to the present embodiment, and FIGS. 3 a,3 b, 3 c and 3 d are diagrams showing other preparation procedures ofscintillator panel 10 panel relating to the present embodiment. FIG. 4is a diagram showing an outline structure of evaporator 60.

Next, preparation procedures of scintillator panel 10 in the presentembodiments will be described.

(Formation of Reflection Layer)

As shown in FIG. 2 a, reflection layer 2 is first formed on support 1.

In addition, support means a member which plays a predominant role inorder to support a phosphor layer as a constituent element for ascintillator panel, and in the case of the present example, a resin filmcapable of being deformed via a heat treatment is preferably used forit.

Examples of the resin film include polyethylene terephthalate,polyethylene naphthalate, cellulose acetate, polyamide, polyimide,epoxy, polyamideimide, bismaleimide, a fluorine resin, acryl,polyurethane, nylon 12, nylon 6, polycarbonate, polyphenylenesulfide,polyethersulfone, polysulfone, polyetherimide, polyether ether ketone, aliquid crystal polymer and so forth.

As to a scintillator panel reflection layer 2 may be formed on thesurface where at least a phosphor layer is vapor-deposited on support 1.When high luminance is demanded for a scintillator, luminance can beimproved since emission of the phosphor can be efficiently taken out byproviding reflection layer 2. Reflection layer 2 preferably has asurface reflectance of 80% or more, and more preferably has a surfacereflectance of 90% or more. A material constituting reflection layer 2preferably contains aluminum, silver, platinum, gold, copper, iron,nickel, chromium, cobalt, stainless steel or the like. Of these, amaterial containing aluminum or silver as a main component isspecifically preferable in view of reflectance and corrosion resistance.When a metal thin film is composed of at least two layers, it ispreferable in view of improved adhesion to a support that a lower layeris preferably is a layer containing Ni or Cr, or both of them. Further,a layer made of SiO₂, TiO₂ or the like may be formed on a metal thinfilm to further improve reflectance.

In addition, when high sharpness is demanded for a scintillator,reflection layer 2 may be omitted.

As a method of coating metal on a support, provided are evaporation,sputtering, attachment of a metal foil and so forth with no specificlimitation, but sputtering is most preferable in view of tight adhesion.

In order to further improve adhesion of reflection layer 2 to support 1,an intermediate layer is preferably provided between reflection layer 2and support 1. Examples of the material constituting an intermediatelayer include easily adhesive polymers, for example, proteins such asgelatin, derivative gelatin, colloidal albumin, casein and so forth;cellulose compounds such as carboxymethyl cellulose, diacetyl cellulose,triacetyl cellulose and so forth; agar, sodium alginate; saccharidederivatives such as starch derivatives and so forth; synthetichydrophilic colloids, for example, vinyl polymers and their copolymerssuch as polyvinyl alcohol, poly-N-vinylpyrrolidone, a polyester resin, apolyacrylic acid polymer, polyacrylamide or their derivatives andhydrolysates, polyvinyl acetate, polyacrylnitrile, polyacrylic acidester and so forth, natural products such as rosin, shellac and so forthand their derivatives, and a large number of other synthetic resins.Further, usable is emulsion such as a styrene-butadiene copolymer, apolyacrylic acid, a polyacrylic acid ester and its derivative, polyvinylacetate, a vinyl acetate-acrylic acid ester copolymer, polyolefin, anolefin-vinyl acetate copolymer or the like. In addition, also usable area carbonate based resin, a polyester based resin, a urethane basedresin, an epoxy based resin, and organic semiconductors such aspolyvinyl chloride, polyvinylidene chloride and polypyrrole. Further,these binders can be used in combination with at least two kindsthereof. In addition, reflection layer 2 preferably has a thickness of0.005-0.3 μm, and more preferably has a thickness of 0.01-0.2 μm in viewof taking-out efficiency of luminescent light.

Besides these, a dissimilar metal to a reflection layer may be formed asan intermediate layer. Preferably used is at least one selected from thegroup consisting of nickel, cobalt, chromium, palladium, titanium,zirconium, molybdenum and tungsten, for example. Of these, nickel andchromium are further preferably used singly, or used in combination.

(Formation of Subbing Layer)

Next, as shown in FIG. 2 b, in order to improve adhesion of a phosphorlayer to a support, subbing layer 3 is preferably provided.

An easily adhesive polymer, for example, is usable for subbing layer 3.Subbing layer 3 preferably has a thickness of 0.2-5.0 μm; morepreferably has a thickness of 0.5-4.0 μm; and still more preferably hasa thickness of 0.7-3.5 μm.

(Formation of Phosphor Layer)

Next, as shown in FIG. 2 c, phosphor layer 4 is formed. Since anevaporator is suitably used in this step, a brief overview of evaporator60 shown in FIG. 4 will be first described.

<Evaporator>

As shown in 4, evaporator 60 is equipped with vacuum chamber 62 in theform of a box, and boat 63 for vacuum evaporation is provided in theinside of vacuum chamber 62. Boat 63 is a member in which an evaporationsource is to be filled, and an electrode is connected to boat 63. Whenan electric current is carried to boat 63 via the electrode, boat 63 isdesigned to be heated by Joule heat. During preparation of scintillatorpanel 10, a mixture containing cesium iodide and an activator compoundis filled in boat 63, and the above-described mixture is designed to beheated and evaporated via electric current flow into boat 63.

In addition, as a member in which an evaporation source is to be filled,an aluminum crucible wound by a heater may be used.

Holder 64 to hold support 1 constituting a scintillator panel isprovided directly above boat 63 inside vacuum chamber 62. Holder 64 isequipped with a heater (unshown in the figure), and support 1 placed onholder 64 is designed to be heated by operating the heater. When heatingsupport 1, it is arranged to be designed that an adsorbate on thesurface of support 1 is released and removed from the surface; formationof an impurity layer between support 1 and a phosphor layer(scintillator layer) formed on the surface of support 1 is inhibited;tight adhesion of the phosphor layer formed on the surface of support 1to support 1 is enhanced; and film quality of the phosphor layer formedon the surface of support 1 is adjusted.

Holder 64 is provided with rotation mechanism 65 to rotate holder 64.Rotation mechanism 65 is equipped with rotating shaft 65 a connected toholder 64 and a motor (unshown in the figure) as a driving source, androtary shaft 65 a is designed to be rotated in the state when holder 64is opposed to boat 63, when the motor is driven.

Vacuum chamber 62 in evaporator 60 is equipped with vacuum pump 66 inaddition to the above-described structure. Vacuum pump 66 evacuates theinside of vacuum chamber 62, and introduces gas into the inside ofvacuum chamber 62. It is designed that the inside of vacuum chamber 62is maintained under gas atmosphere at a given pressure, when operatingvacuum pump 66.

As to formation of phosphor layer 4 shown in FIG. 2 c, substrate 1 onwhich reflection layer 2 and subbing layer 3 are formed is placed onholder 64, and a powdered mixture containing cesium iodide and anadditive containing a thallium compound is filled in boat 63. In thiscase, a distance between boat 63 and support 1 is set to 100-1500 mm,and a treatment of the after-mentioned evaporation process is preferablyconducted while remaining within the setting range.

Next, the inside of vacuum chamber 62 is evacuated by operating vacuumpump 66 to obtain a vacuum atmosphere of 0.1 Pa or less in the inside ofvacuum chamber 62. herein, “vacuum atmosphere” means atmosphere having apressure of 100 Pa or less, and an atmosphere pressure of 0.1 Pa or lessis preferable.

Thereafter, inert gas such as argon or the like is introduced into theinside of vacuum chamber 62, and vacuum atmosphere inside vacuum chamber62 is maintained at 0.001-5 Pa, and preferably at 0.01-2 Pa. Support 1having been placed on holder 64, which is opposed to boat 63, is rotatedwhile heating by operating a heater for holder 64 and rotation mechanism65. Temperature of support 1 on which phosphor layer 4 is to be formedis preferably set to a room temperature of 25° C. to 50° C. at the startof evaporation. During evaporation, a temperature of 100-300° C. ispreferable, and a temperature of 150-250° C. is more preferable.

In this situation, an electric current is carried to boat 63 from anelectrode, and a mixture containing cesium iodide and an additivecontaining a thallium compound is heated at about 700-800° C. for apredetermined duration to vaporize the mixture. As a result, a largenumber of columnar crystals 4 a are sequentially grown on the surface ofsubbing layer 3 provided above support 1 to form phosphor layer 4 havinga desired thickness.

Commonly known various phosphor materials are usable as the material toform phosphor layer 4, but since a conversion ratio from X-rays intovisible light is considerably high, and phosphor can be formed easily inthe form of a columnar crystal structure via evaporation, scattering ofluminescent light inside crystals are inhibited by an optical guideeffect, and thickness of the phosphor layer can be increased, wherebycesium iodide (CsI) is preferably used.

However, since CsI used singly exhibits low emission efficiency, variousactivated materials are added therewith. For example, one in which CsIand sodium iodide (NaI) are mixed at an arbitrary molar ratio providedas disclosed in Japanese Patent Examined Publication No. 54-35060.Further, for example, as to CsI disclosed in Japanese Patent O.P.I.Publication No. 2001-59899, CsI containing an activation material suchas indium (In), thallium (Tl), lithium (Li), Potassium (K), rubidium(Rb), sodium (Na) or the like via evaporation is preferable.

Use of cesium iodide and an additive containing a thallium compound asraw material is preferable. That is, thallium-activated cesium iodide(CsI:Tl) having a wide range emission wavelength of 400-750 nm ispreferable.

Various thallium compounds (compound having an oxidation number of 1⁺and compound having an oxidation number of 3⁺) are usable as thethallium compound for an additive containing thallium iodine (TlI),thallium bromide (TlBr), thallium chloride (TlCl) and so forth arepreferable.

Further, in order to obtain additives evenly present inside a phosphorlayer (inside columnar crystals), a melting point of the thalliumcompound preferably falls within the range of 400-700° C. In addition,the melting point means a melting point at normal temperatures andpressures.

As to a phosphor layer in the present embodiment, a content of theadditives should be set to a most appropriate amount depending on thepurpose, performance and so forth, but in order to maintain emissionluminance and property•function of cesium iodide, the additives have acontent of 0.01-50 mol %, and preferably have a content of 0.1-10.0 mol%, based on the content of cesium iodide. In addition, in order toobtain properties of luminance and sharpness in a balanced manner, thephosphor layer preferably has a thickness of 100-800 μm, and morepreferably has a thickness of 120-700 μm.

As described above, phosphor layer 4 is formed on support 1 to preparescintillator panel 10.

In addition, as to scintillator panel 10, after forming a phosphor layeron a support layer larger than a product in size, a step of cutting thesupport into the product size for the scintillator is preferablyarranged to be set. Productivity is improved by cutting plural pieces ofproducts out of a large support on which a phosphor layer is formed.Examples of a method of cutting a scintillator panel include punchingwith a blade, press-cutting with a cutter, cutting with scissors,cutting with laser light and so forth.

As described above, protrusions caused by anomalous growth of evaporatedphosphor crystals, which are originated from dust or the like, tend tobe generated in the resulting scintillator panel 10, when formingphosphor layer 4 in FIG. 2 c.

Next, repairing of protrusions in preparation procedures of scintillatorpanel 10 in the present embodiment will be described referring to FIGS.3 a, 3 b, 3 c and 3 d.

(Repairing of Protrusions)

Columnar crystals 4 b as protrusions obtained via anomalous growth ofevaporated phosphor crystals originated from dust or the like are formedin scintillator panel 10 shown in FIG. 3 a. Columnar crystals 4 b arerepaired as described below.

Scintillator panel 10 is sandwiched by rigid plate 31 on the backsurface side of support 1 and rigid plate 32 on the front surface ofphosphor layer 4 as shown in FIG. 3 b, and rigid plates 31 and 32 aresubjected to a heat treatment under applied pressure in the arrowdirection in the figure.

As a method of applying a pressure, there are applied pressure by usinga weight, mechanically applied pressure and so forth, and there is nospecific limitation, but a sealing and depressurizing method employing aheat-resistant plastic film container in the form of a bag ispreferable. More specifically, after sandwiching the scintillator panelwith rigid plate 31 on the back surface side of support 1 and rigidplate 32 on the front surface side of phosphor layer 4, the resulting isstored in the plastic film container, and this container is sealed anddepressurized to apply a pressure by atmospheric pressure. This methodby which a pressure can be evenly applied to the rigid plate easily, andan amount of applied pressure can be easily adjusted by adjusting anamount of reduced pressure inside this container is preferable.

Further, an amount of applied pressure is preferably 0.001-10 MPa, andpreferably 0.01-1 MPa. In the case of an amount of applied pressure of0.001 or more, protrusions can be sufficiently displaced to the resinlayer side. On the other hand, in the case of an amount of appliedpressure of 10 MPa or less, damages to phosphor can be suppressed,whereby no image is deteriorated.

Heat treatment temperature is preferably 50-200° C., and more preferably90-160° C. In the case of a heating temperature of 50° C. or more,protrusions can be easily displaced to the resin layer side. On theother hand, in the case of a heating temperature 200° C. or less,influence to images such as reduced luminance or the like can besuppressed.

In addition, “rigid plate” and “one exhibiting stiffness” in the presentexample, mean a plate having an elastic modulus of 10 GPa or more, andmetal, glass, carbon, a composite material and so forth are usable withno specific limitation, but glass is preferable in view of excellentflatness of the surface. The flatness range of the rigid platepreferably has a center line average roughness Ra of 0-0.5 μm, and morepreferably has a center line average roughness Ra of 0-0.1 μm.

Two rigid plates 31 and 32 sandwiching support 1 and phosphor layer 4each may be made of material identical to each other, or different fromeach other. Further, rigid plate 31 provided on the support 1 side maybe a support to support scintillator panel 10.

Scintillator panel 10 after removing rigid plates 31 and 32 fromscintillator panel 10 after applying a pressure and conducting a heattreatment as described above results in the state shown in FIG. 3 c.

As shown in FIG. 3 c, columnar crystal 4 b as a protrusion, as it is, isdisplaced to the support 1 side, and pulled into subbing layer 3,reflection layer 2 and support 1. Protrusions on the front surface sidewhich are displaced to the support 1 side end up with approximatelyuniform height, whereby the surface of phosphor layer 4 is flattened.

That is, repairing of protrusions in the present example means thatheight on the front surface side is uniformized by conducting a heattreatment under applied pressure after sandwiching scintillator panel 10with rigid plates 31 and 32 to displace columnar crystal 4 b to theresin section side on the support 1 side, and since protrusions areforcibly deformed or removed therefrom, generation of dust is possibleto be eliminated via repairing.

In many cases, protrusions have a height of approximately 10-100 μm.Therefore, the resin section on the support 1 side preferably has atotal thickness of 10 μm or more; more preferably has a total thicknessof 50 μm or more; and still more preferably has a total thickness of 150μm or more. In order to produce the effect of the present invention,there is specifically no upper limit to the total thickness of a resinlayer, but the resin layer preferably has a total thickness of 2 mm orless in view of no deterioration of roentgenoparency.

(Formation of Protective Layer)

CsI to form phosphor layer 4 exhibiting moisture-absorption deliquencesvia absorption of water vapor when the CsI remains exposed. Accordingly,in order to avoid the foregoing, a protective layer is formed so as tocover a phosphor layer. FIG. 3 d shows the state where protective layer5 is formed after repairing the above-described protrusions.

In order to form a protective layer, it is preferable to form it with aresin film, or to form it by a CVD method.

In the case of a CVD method, a protective layer is preferably formed bycovering the entire surface of a scintillator panel with apolyparaxylene resin film. Polyparaxylene is penetrated into gapspresent in columnar crystals of CsI by using a CVD method to tightlyattach a protective layer onto CsI.

The polyparaxylene resin film is not specifically limited, but thepolyparaxylene resin film having a thickness of 1-30 μm is preferablyformed on the surface of at least a phosphor layer. In the case of apolyparaxylene resin film having a thickness of 1 μm or more, highermoisture-preventing effect is produced, and in the case of apolyparaxylene resin film having a thickness of 30 μm or less,degradation of MTF can be suppressed. In addition, a polyparaxyleneresin film having a thickness of 5-30 μm is more preferable, and apolyparaxylene resin film having a thickness of 5-10 μm is still morepreferable.

Further, a resin film may be provided on a phosphor layer as aprotective layer for the protective layer in another embodiment. Inaddition, “resin film” means a (ready-made) resin film formed in advancebefore preparing a scintillator panel, unless otherwise specificallymentioned.

The resin film as a protective layer preferably has a thickness of12-100 μm, and more preferably has a thickness of 20-60 μm in view ofprotection of a phosphor layer, sharpness, moisture-resistance,workability and so forth. Further, a haze ratio is preferably 3-40%, andmore preferably 3-10% in view of sharpness, unevenness of radiationimages, manufacturing stability, workability and so forth. “Haze ratio”refers to values determined by NDH 5000W of Nippon Denshoku IndustriesCo., Ltd. Resin films having a desired haze ratio are appropriatelyselected from commercially available resin films, and possible to beeasily obtained.

The resin film or the like as a protective layer preferably has a lighttransmittance of 70% or more at a wavelength of 550 nm in considerationof photoelectric conversion efficiency, emission wavelength and soforth, but since films having a light transmittance of 99% or more areindustrially difficult to be obtained, a light transmittance of 70-99%is practically preferable.

Taking into consideration protection and deliquescence of thescintillator layer, the protective film preferably has a moisturepermeability (measured in accordance with JIS Z0208) of 50 g/m²·day orless (at 40° C. and 90% RH) and more preferably a moisture permeability(measured in accordance with JIS Z0208) of 10 g/m²·day (at 40° C. and90% RH) or less, but since no film having a moisture permeability of0.01 g/m²·day or less (at 40° C. and 90% RH) is industrially available,a moisture permeability (measured in accordance with JIS 20208) of0.01-50 g/m²·day (at 40° C. and 90% RH) is preferable, and a moisturepermeability (measured in accordance with JIS Z0208) of 0.1-10 g/m²·day(at 40° C. and 90% RH) is more preferable.

A radiation image detector in which scintillator panel 10 prepared bythe above-described manufacturing method is attached onto aphotoelectric conversion panel possessing a photoelectric conversionelement will be described.

FIG. 5 is an oblique perspective view accompanied with a partlybroken-out section showing an outline structure of radiation imagedetector 100. FIG. 6 an enlarged cross-sectional view of imaging panelsection 51.

As shown in FIG. 5, radiation image detector 100 is equipped withimaging panel 51, controller 52 to control action of radiation imagedetector 100, memory section 53 as a memory device to store imagesignals output from imaging panel 51 employing a rewritable dedicatedmemory (flash memory, for example), power supply section 54 as apower-supplying device to supply an electric power necessary to obtainimage signals via driving of imaging panel 51 and so forth in enclosure55. Enclosure 55 is provided with communication purpose connector 56 tocommunicate from radiation image detector 100 to the outside, operationsection 57 to switch action of radiation image detector 100, displaysection 58 for displaying that imaging preparation of radiation imagesis completed, and a predetermined amount of image signals has beenwritten in memory section 53, and so forth, if desired. In addition,radiation image detector 100 may be a communication section for wirelesscommunication in place of connector 56 for communication.

As shown in FIG. 6, imaging panel 51 is equipped with scintillator panel10, and photoelectric conversion panel 20 to output image signals viaabsorption of electromagnetic waves from scintillator panel 10.

Scintillator panel 10 is placed on the radiation-irradiating plane side,and is arranged to be designed so as to emit electromagnetic wavesdepending on intensity of incident radiation.

Photoelectric conversion panel 20 is provided on the surface opposite tothe radiation-irradiated surface of scintillator panel 10 for radiation,and possesses barrier film 20 a, photoelectric conversion element 20 b,image signal output layer 20 c and substrate 20 d in this order from theside of scintillator panel 10 for radiation.

Bather film 20 a is provided to separate scintillator panel 10 forradiation from other layers.

Photoelectric conversion element 20 b possesses transparent electrode21, charge generation layer 22 to generate charge by being excited withelectromagnetic waves having been incident via transmission oftransparent electrode 21, and counter electrode 23 as an electrodeopposite to transparent electrode 21, and possesses transparentelectrode 21, charge generation layer 22 and counter electrode 23 inthis order from the side of bather film 20 a.

Charge generation layer 22 is formed on the one surface side oftransparent electrode 21 in the form of a thin film, and also containsan organic compound to be charge-separated by light as aphotoelectrically convertible compound, and contains conductivecompounds as an electron acceptor and an electron donor capable ofgenerating charge, respectively. In charge generation layer 22, electrondonors are excited upon incident electromagnetic waves to releaseelectrons, and released electrons are moved to electron acceptors togenerate charge inside charge generation layer 22, that is, holes andelectrons as carriers.

Charge generation layer 22 preferably has a thickness of 10 nm or more(specifically, 100 nm or more) in view of acquisition of an amount oflight absorption, and also preferably has a thickness of 1 μm or less(specifically, 300 nm or less) in view of no generation of too largeelectrical resistance.

Counter electrode 23 is placed on the side opposite to the plane on theside where electromagnetic waves of charge generation layer 22 areincident.

Further, a buffer layer may be provided between electrodes (transparentelectrode 21 and counter electrode 23) sandwiching charge generationlayer 22 in order to be acted as a buffer zone in such a way that chargegeneration layer 22 and each of these electrodes are not reacted.

Image signal output layer 20 c is one to output a signal based onstorage of charge obtained in photoelectric conversion element 20 b aswell as stored charge, and possesses condenser 24 as a charge storageelement to store charge produced in photoelectric conversion element 20b for each pixel, and transistor 25 as an image signal output element tooutput stored charge as a signal.

Transistor 25 stores charge generated in photoelectric element 20 b, andan accumulated electrode (unshown in the figure) as one electrode forcondenser 24 is electrically connected to the transistor. Condenser 24stores charge produced in photoelectric element 20 b, and this storedcharge us read by driving transistor 25. That is, the signal for eachpixel of the radiation image can be output by driving transistor 25.

Substrate 20 b serves as a support for imaging panel 51.

Next, action of radiation image detector 100 will be described.

As to radiation incident to radiation image detector 100, the radiationenters toward rge substrate 20 d side from the scintillator panel 10side for radiation.

By this, as to radiation incident to scintillator panel 10 forradiation, phosphor layer 4 in scintillator panel 10 absorbs energy ofthe radiation, and electromagnetic waves are emitted depending on theintensity. Electromagnetic waves entering photoelectric conversion panel20, of emitted electromagnetic waves pass through bather film 2 a inphotoelectron conversion panel 20, and transparent electrode 21, andreach charge generation layer 22. Then, electromagnetic waves areabsorbed in charge generation layer 22, and a pair of a hole and anelectron (charge separation state) is formed depending on the intensity.

Thereafter, holes and electrons are carried to different electrodes,respectively, with internal electric field produced via application of abias voltage from power supply section 54, and photocurrent flows.

Then, holes having been carried to the counter electrode 23 side arestored in condenser 24 of image signal output layer 20 c. Stored holesoutput image signals when driving transistor 25 connected to condenser24, and output image signals are recorder in memory section 53.

Since radiation image detector 100 explained herein is equipped withscintillator panel 10 prepared by the above-described manufacturingmethod, it becomes possible to provide a radiation image detectorexhibiting no image defects but excellent image quality.

EXAMPLE

The following Examples will be described.

Preparation of Example 1

Silver was sputtered onto a resin layer made of polyimide (UPILEX S,produced by UBE INDUSTRIES. LTD.) having a thickness of 125 μm as asupport so as to provide a reflection layer having a thickness of 70 nm,and a polyester resin (VYLON 200, produced by TOYOBO CO., LTD.)dissolved in methyethyl ketone was subsequently coated employing a spincoater, followed by drying to provide a subbing layer having a dry filmthickness of 3.0 μm. Thereafter, the resulting was cut in 100 mm×100 mmsize to prepare a support.

Next, phosphor (CsI: 0.003Tl) was vapor-deposited onto the surface onthe subbing layer side of the support employing an evaporator shown inFIG. 4 to form a phosphor layer.

That is, the above-described phosphor raw material as an evaporationmaterial was first filled in a resistance heating crucible (board), anda support was placed onto a metal frame of a rotation holder to adjust adistance between the support and an evaporation source to 400 mm.

After the inside of an evaporator was subsequently evacuated once, and avacuum degree was adjusted to 0.5 Pa by introducing Ar gas therein,temperature was maintained at 200° C. while rotating the support at 10mm. Next, resistance heating crucible (board) was heated to evaporatephosphor, and when the layer thickness reached 450 μm, evaporationthereof was terminated.

A glass plate (EAGLE2000 or EAGLE XG, produced by Corning Inc.) as arigid plate was layered on each of the support surface and the phosphorsurface, and the system was subjected to a heat treatment at 100° C. for2 hours in a state where a weight load of 0.05 MPa was applied.

After removal of two rigid plates, a moisture-resistant film having thefollowing structure was employed to protect the phosphor layer side.

NY 15///VMPET12///VMPET12///PET 12///CPP 20

when NY: Nylon,

PET: Polyethylene terephthalate,

CPP: Casting polypropylene, and

VMPET: Alumina-evaporated PET (commercially available product, producedby Toyo Metalizing Co., Ltd.). The number described behind the name ofeach resin represents layer thickness of the resin layer (in μm).

“///” represents a dry lamination adhesive layer of 3.0 μm in thickness.A two liquid reaction type urethane based adhesive was used as anadhesive for the utilized dry lamination.

The protective film on the back surface side of the support is a drylamination film composed of a 30 μm thick CPP film, a 9 μm thickaluminum film, and a 188 μm thick polyethylene terephthalate film.Further, the adhesive layer has a thickness of 1.5 μm, and a two liquidreaction type urethane based adhesive was used in this case.

The peripheral portion was fused, and sealed by the above-describedmoisture-resistant film and a protective film employing an impulsesealer under reduced pressure to prepare a scintillator panel.

In addition, fusion was carried out so as to make a distance from afused section to the peripheral portion of the phosphor plate to be 1mm. As a heater for the impulse sealer used for fusion, used is a 3 mmwide heater.

A radiation image detector was prepared employing a scintillator panelprepared under the above-described conditions.

Preparation of Example 2

When a glass plate (EAGLE2000 or EAGLE XG, produced by Corning Inc.) waslayered on each of the support surface and the phosphor surface, a hotmelt sheet (NP608, produced by Sony Chemicals Corp.) was insertedbetween the back surface of the support and the glass plate produced byCorning Inc., and a heat treatment was carried out at 100° C. for 2hours similarly in the state where a weight load of 0.05 MPa wasapplied. By conducting the treatment, the support and glass on the backsurface are joined via the hot melt sheet.

After removal of the glass on the phosphor side, a radiation imagedetector was prepared similarly to Example 1, employing a scintillatorpanel in which a protective layer was formed.

Preparation of Example 3

A polyester resin (VYLON200, produced by TOYOBO CO. LTD.) dissolved inmethylethyl ketone was coated on a high reflection aluminum plate (MIRO2LCD, produced by ALANOD Aluminium-Veredlung GmbH & Co. KG) of 100 mm×100mm in size as a support, followed by drying to provide a subbing layerhaving a dry layer thickness of 15 μm.

Phosphor (CsI: 0.003Tl) was subsequently vapor deposited onto thesupport surface employing an evaporator shown. in FIG. 4 under the samecondition as in Example 1 to form a phosphor layer.

Thereafter, a glass plate (EAFLE2000 or EAGLE XG) was layered onto thesurface on the phosphor side, and a heat treatment was carried out at100° C. for 2 hours in the state where a weight load of 0.05 MPa wasapplied.

After removal of the glass, a radiation image detector was preparedunder the same condition as in Example 1, employing a scintillator panelin which a protective layer was formed.

That is, in the case of Example 3, an aluminum plate having stiffness isused as a support, and is designed to serve as a rigid plate provided onthe support side during application of pressure, and heating. Inaddition, a rigid plate may be used on the support side withoutemploying the aluminum plate serving as a rigid plate provided on thesupport side.

Preparation of Example 4

A radiation image detector was prepared under the same condition as inExample 1, except that a resin layer as a support made of polyamide(UPILEX S, produced by UBE INDUSTRIES, LTD) having a thickness of 50 μm.

Preparation of Example 5

A polyester resin (VYLON200, produced by TOYOBO CO. LTD.) dissolved inmethylethyl ketone was coated on a high reflection aluminum plate (MIRO2LCD, produced by ALANOD Aluminium-Veredlung GmbH & Co. KG) of 100 mm×100mm in size as a support, followed by drying to provide a subbing layerhaving a dry layer thickness of 3.0 μm.

A radiation image detector was prepared under the same condition asdescribed in Example 3, except that the subbing layer was provided asexplained above.

Preparation of Example 6

A polyester resin (VYLON 200, produced by TOYOBO CO., LTD.) dissolved inmethyethyl ketone was coated on polyimide (UPILEX S, produced by UBEINDUSTRIES. LTD.) having a resin layer thickness of 125 μm as a supportemploying a spin coater, followed by drying to provide a subbing layerhaving a dry film thickness of 3.0 μm. Thereafter, the resulting was cutin 100 mm×100 mm size to prepare a support.

Next, phosphor (CsI: 0.003Tl) was vapor-deposited onto the surface onthe subbing layer side of the support employing an evaporator shown inFIG. 4 to form a phosphor layer.

A glass plate (EAGLE2000 or EAGLE XG, produced by Corning Inc.) as arigid plate was layered on each of the support surface and the phosphorsurface, and the system was subjected to a heat treatment at 100° C. for2 hours in a state where a weight load of 0.05 MPa was applied.

After removal of the rigid plate, it was exposed to the vapor obtainedby sublimating polyparaxylene raw material (dix-C, produced by KISCOLTD.), and a scintillator panel was prepared on the entire surface of aphosphor layer by coating a polyparaxylene resin film having a thicknessof 3 μm to similarly prepare a radiation image detector.

Preparation of Comparative Example 1

A scintillator panel was produced to prepare a radiation image detectorsimilarly to Example 1, except that application of pressure with rigidplates and heating among the conditions in Example 1 were only omitted.

Seven conditions of Example 1, Example 2, Example 3, Example 4, Example5, Example 6 and Comparative example 1 as described above, andevaluation results thereof are collectively shown in Table 1.

TABLE 1 Total The Subbing Adhesive thickness number layer Support layerto of of (Resin Resin rigid Rigid plate resin pixel layer) thicknessplate Phosphor Support layers defects *a *c *d Material (μm) *c *d sideside (μm) (number) *b Ex. 1 (*2) 3 Polyimide (*3) 125 — 0 Glass (*1)Glass (*1) 128 2 A Ex. 2 (*2) 3 Polyimide (*3) 125 (*4) 50 Glass (*1)Glass (*1) 178 0 A Ex. 3 (*2) 15 Aluminum (*5) 0 — 0 Glass (*1) Aluminum(*5) 15 7 B Ex. 4 (*2) 3 Polyimide (*3) 50 — 0 Glass (*1) Glass (*1) 534 A Ex. 5 (*2) 3 Aluminum (*5) 0 — 0 Glass (*1) Aluminum (*5) 3 25 C Ex.6 (*2) 3 Polyimide (*3) 125 — 0 Glass (*1) Glass (*1) 128 2 A Comp. 1(*2) 3 Polyimide (*3) 125 — 0 — — 128 78 D Ex.: Example Comp.:Comparative example *a: Scintillator panel *b: Evaluation *c: Material*d: Thickness (μm) (*1): EAGLE2000 or EAGLE XG, produced by Corning Inc.(*2): VYLON 200, produced by TOYOBO CO., LTD. (*3): UPILEX S, producedby UBE INDUSTRIES. LTD. (*4): NP608, produced by Sony Chemicals Corp.(hot melt sheet) (*5): MIRO2 LCD, produced by ALANOD Aluminium-VeredlungGmbH & Co. KG

The number of pixel defects is one obtained by counting the number ofdefects exceeding ±5% from the mean signal value of image data acquiredby exposing a radiation image detector to X-rays having a tube voltageof 80 kVp.

As to evaluation criteria shown in Table 1, when the number of pixeldefects was less than 5, the rank was set to “A”; when the number ofdefects was not less than 5 and less than 10, the rank was set to “B”;when the number of defects was not less than 10 and less than 30, therank was set to “C”; and when the number of defects was not less than30, the rank was set to “D”.

As shown in Table 1, it can be understood that it is effective forreducing the number of pixel defects to conduct a heat treatment underapplied pressure after conducting the sandwiching step with the rigidplates. Further, the total thickness of resin layers as the sum of thethickness of resin sections provided between a phosphor layer and arigid plate on the support side is not less than 10 μm, and in the caseof a radiation image detector fitted with a scintillator panel havingbeen subjected to a heat treatment under applied pressure afterconducting the sandwiching step with the rigid plates, the number ofpixel defects becomes less than 10, whereby it is to be understood thatan excellent radiation image detector exhibiting the reduced number ofpixel defects has been obtained.

Further, in the case of a radiation image detector fitted with ascintillator panel possessing the steps of conducting a heat treatmentunder applied pressure after conducting the sandwiching step with therigid plates, and having a total thickness of resin layers of 50 μm, thenumber of pixel defects becomes less than 5, whereby it is to beunderstood that a better radiation image detector has been obtained.

In addition, in the above-described embodiment, explanations have beenmade by utilizing an example in which a step of conducting a heattreatment under applied pressure after conducting the sandwiching stepwith the rigid plates is applied to one in which a phosphor layer isformed from columnar crystals, but the present invention is not limitedthereto, and an example in which the step of conducting a heat treatmentunder applied pressure after conducting the sandwiching step with therigid plates is also applicable to a coating type scintillator panel inwhich phosphor particles are mixed with binder to coat the resulting ona support.

EXPLANATION OF NUMERALS

-   1 Support-   2 Reflection layer-   3 Subbing layer-   4 Phosphor layer-   5 Protective layer-   10 Scintillator panel-   20 Photoelectric conversion panel-   20 b Photoelectric conversion element-   31, 32 Rigid plate-   51 imaging panel-   60 Evaporator-   100 Radiation image detector

The invention claimed is:
 1. A method of manufacturing a scintillatorpanel comprising a support having a phosphor layer formed thereon, themethod comprising: forming the phosphor layer on the support, andsubsequently heat-treating the support and the phosphor layer while thesupport and the phosphor layer are sandwiched by two rigid plates underapplied pressure.
 2. The method of claim 1, wherein the scintillatorpanel comprises a resin section excluding the phosphor layer, and theresin section has a total thickness of 10 μm or more.
 3. The method ofclaim 1, wherein the support comprises polyimide as a main component. 4.The method of claim 1, further comprising: storing the support and thephosphor layer sandwiched by the two rigid plates in a plastic filmcontainer; and sealing and depressurizing the plastic film container toconduct the applied pressure.
 5. The method of claim 1, furthercomprising covering the phosphor layer with a protective layer.
 6. Themethod of claim 5, wherein the protective layer comprises a resin film.7. The method of claim 5, wherein the protective layer comprises apolyparaxylene resin film formed by a CVD method.
 8. The method of claim1, wherein the phosphor layer comprises columnar crystals.
 9. The methodof claim 8, further comprising: evaporating cesium iodide and anadditive containing a thallium compound as raw materials to form thephosphor layer.
 10. A scintillator panel prepared by the method ofclaim
 1. 11. A radiation image detector comprising the scintillatorpanel of claim 10 attached onto a photoelectric conversion panelcomprising a photoelectric conversion element.
 12. A method ofmanufacturing a scintillator panel comprising a support exhibitingstiffness and having a phosphor layer formed thereon, the methodcomprising: forming the phosphor layer on the support, and subsequentlyheat-treating the phosphor layer while the phosphor layer is sandwichedby the support and a rigid plate under applied pressure.
 13. The methodof claim 12, wherein the scintillator panel comprises a resin sectionexcluding the phosphor layer, and the resin section has a totalthickness of at least 10 μm.
 14. The method of claim 12, wherein thesupport comprises polyimide as a main component.
 15. The method of claim12, further comprising: storing the phosphor layer sandwiched by thesupport and the rigid plate in a plastic film container; and sealing anddepressurizing the plastic film container to conduct the appliedpressure.
 16. The method of claim 12, further comprising covering thephosphor layer with a protective layer.
 17. The method of claim 16,wherein the protective layer comprises a resin film.
 18. The method ofclaim 16, wherein the protective layer comprises a polyparaxylene resinfilm formed by a CVD method.
 19. The method of claim 12, wherein thephosphor layer comprises columnar crystals.
 20. The method of claim 19,further comprising: evaporating cesium iodide and an additive containinga thallium compound as raw materials to form the phosphor layer.
 21. Ascintillator panel prepared by the method of claim
 12. 22. A radiationimage detector comprising the scintillator panel of claim 21 attachedonto a photoelectric conversion panel comprising a photoelectricconversion element.